Combination crane

Abstract

A combination crane A is formed by connecting two crawler cranes 1 L and 1 R. Each crawler crane is provided with at least a lower propelling body 3 which can be propelled by crawlers 2 , an upper revolving body 5 rotatably mounted on the lower propelling body 3 by a swing unit 4 provided between them, a boom 6 whose base section is tiltably supported on the upper revolving body, a tilting mechanism 10 that raises and lowers the boom and a hoist mechanism that hoists and lowers the lifting members 12 hung by a hoist rope 11 from the top of the boom. Both upper swing bodies of two cranes are connected together with a connecting beam 20 . Swing motion is performed by driving the one crawler crane to move around the other crawler crane which is free to rotate and is locked against propulsion.

1. A combination crane used for crane operation, comprising:
 two crawler cranes, each of said crawler cranes respectively comprising a lower propelling body having crawlers, an upper revolving body rotatably mounted on said lower propelling body, a boom whose base section is tiltably supported on said upper revolving body, a tilting mechanism that hoists and lowers said boom, and a hoist mechanism that hoists and lowers a lifting member hung by a hoist rope from a top of said boom; 
 a connecting beam which connects said upper revolving bodies of said two crawler cranes; and 
 means for controlling swinging and propelling of said combination crane by stopping the crawlers of the lower propelling body of one of said two crawler cranes, unlocking the upper revolving body of the one of said two crawler cranes such that the upper revolving body of the one of said two crawler cranes can rotate relative to the lower revolving body of the one of said two crawler cranes, locking the upper revolving body of the other of said two crawler cranes such that the upper revolving body of the other of said two crawler cranes cannot rotate relative to the lower revolving body of the other of said two crawler cranes, and operating the crawlers of the lower propelling body of the other of said two crawler cranes such that the other of the two crawler cranes swings around the one of the two crawler cranes, 
 wherein said connecting beam is rotatably connected to both of said upper revolving bodies of said two crawler cranes so as to rotate around an approximately horizontal axis. 
 
   
   
     2. The combination crane according to  claim 1 , wherein
 said connecting beam is rotatably connected to said upper revolving body of said other of said two crawler cranes so as to rotate around an approximately vertical axis. 
 
   
   
     3. The combination crane according to  claim 1 , wherein
 said connecting beam is able to allow telescopic movement along an axial direction of said connecting beam. 
 
   
   
     4. The combination crane according to  claim 1 , wherein
 said connecting beam is rotatably connected to said upper revolving body of said other of said two crawler cranes so as to rotate around an approximately vertical axis, and 
 said connecting beam is able to allow telescopic movement along an axial direction of said connecting beam. 
 
   
   
     5. The combination crane according to  claim 4 , further comprising:
 a load detecting means for detecting a load of a lifting material suspended by lifting members, said load detecting means respectively provided on both of said crawler cranes; and 
 a master hoisting control means for controlling said hoist mechanisms of said crawler cranes so as to keep a difference of said loads respectively detected by said load detecting means of said crawler cranes within a predetermined range, said master hoisting control means receiving signals from said load detecting means. 
 
   
   
     6. The combination crane according to  claim 4 , further comprising:
 a boom angle detecting means for detecting a boom angle, said boom angle detecting means respectively provided on both of said crawler cranes; and 
 a master tilting control means for controlling said tilting mechanisms of said crawler cranes so as to keep a difference of said angles respectively detected by said boom angle detecting means of said crawler cranes within a predetermined range, said master tilting control means receiving signals from said boom angle detecting means. 
 
   
   
     7. The combination crane according to  claim 4 , further comprising:
 a beam angle detecting means for detecting a beam angle of said connecting beam around said approximately vertical axis; 
 a swing angle detecting means for detecting a swing angle of said upper revolving body of said one of said crawler cranes; and 
 a parallel propelling means for controlling both of said crawler cranes to propel in parallel, basing on angles detected by said beam angle detecting means and said swing angle detecting means. 
 
   
   
     8. The combination crane according to  claim 4 , further comprising:
 a beam length detecting means for detecting a length of said connecting beam; 
 a swing angle detecting means for detecting a swing angle of said upper revolving body of said one of said crawler cranes; and 
 a parallel propelling means for controlling both of said crawler cranes to propel in parallel, basing on a swing angle detected by said swing angle detecting means and a length detected by said beam length detecting means. 
 
   
   
     9. The combination crane according to  claim 4 , further comprising
 a beam length detecting means for detecting a length of said connecting beam, 
 wherein said means for controlling swinging and propelling of said combination crane operates the crawlers of the lower propelling body of the other of said two crawler cranes based on a length of said connecting beam detected by said beam length detecting means. 
 
   
   
     10. The combination crane according to  claim 9 , further comprising
 a beam angle detecting means which detects a swing angle of said connecting beam around said approximately vertical axis. 
 
   
   
     11. The combination crane according to  claim 10 , wherein
 said means for controlling swinging and propelling of said combination crane controls said lower propelling body of at least one of said two crawler cranes based on a beam angle detected by said beam angle detecting means.